The present invention relates to sound barriers, such as sound-absorbing walls.
In recent years, state highway commissions or transportation departments have promulgated noise level standards for highways passing through urban neighborhoods. As population densities in urban areas increase, it is a virtual certainty that residential neighborhoods will be adjacent a high speed throughway. Even in suburban areas, the desire for ready access to highways and interstates prompts residential development in close proximity to these roads.
Highway noise can greatly impact quality of life for the nearby residents. The federal Environmental Protection Agency has determined that noise levels above 66 decibels are unsafe for residential areas, while 72 dB is the limit for commercial environments. It has been suggested that high decibel levels along the highways may be linked to hearing loss, high blood pressure, irritability, ulcers, and heartburn, among other ailments. A standard pickup truck at 50 mph produces noise at 70 dB, while a medium truck is twice as loud at 80 dB. A motorcycle can reach 90 dB, which is four times louder than the pickup truck.
Highway noise is not only a function of the inherent noisiness of each vehicle. For instance, highway noise doubles when the traffic increases from 200 vehicles per hour to 2000 vehicles per hour, or when traffic speed increases from 30 mph to 65 mph. A single semi-trailer truck at 55 mph produces as much noise as ten cars at the same speed. It is not hard to see that highway noise in densely populated urban environments can quickly become unbearable.
Many approaches have been devised to address the problem of road noise. Some noise abatement systems involve designing the roads themselves to reduce vehicle noise. Lower highway speed limits within city limits can reduce noise. For new development, buffer zones are provided between the residential or commercial buildings and the highway. But for many older neighborhoods, traffic volume has steadily increased over the years as the traffic flow on the adjacent roads has increased. For these neighborhoods, sound barriers are the most viable solution.
Effective noise abatement systems can reduce sound levels 10-15 dB, cutting the loudness of the traffic in half. Where space permits, earth barriers are relative inexpensive and can be used to improve the ecological aesthetics of the neighborhood. This approach is common for new neighborhoods but not often available for existing residential areas. Walls, on the other hand, take up less space. Generally, such walls are limited to 25 feet in height for structural and aesthetic reasons. Noise walls may be built from wood, stucco, concrete, masonry, metal and similar materials.
Concrete sound barrier walls are frequently used because they require only minimal continuing upkeep and are very weather resistant. Moreover, the ability to produce pre-fabricated concrete panels can simplify construction, while also providing the ability to add aesthetic features to the panels.